<!DOCTYPE html>
<html>
	<head>
		<meta charset="UTF-8">
		<title></title>
		<style type="text/css">
			body{
				margin: 0;
				padding: 0;
			}
			.box1{
				width: 600px;
				height: 400px;
				margin: 100px auto;
				background-color: grey;
				border: 1px solid grey;
			}
			.box2{
				width: 400px;
				height: 200px;
				margin: 50px auto;
				background-color: green;
				position: relative;
				left: 100px;
			}
			.box3{
				width: 100px;
				height: 100px;
				background-color: red;
				position: absolute;
				left: 100px;
			}
		</style>
	</head>
	<body>
		<!--emmet
			div.box1>div.box2>div.box3按住Tab键
		-->
		<div class="box1">
			<div class="box2">
				<div class="box3"></div>
			</div>
		</div>
		
	</body>
</html>
